58 
wide group of such experts last summer, and they agreed that the pro- 
posed recombinants could not be as dangerous as many known disease 
producing organisms, which are cultured in thousands of medical lab- 
oratories ever}’ day. 
Fourth, the" bacteria being used in this work are special, weakened 
strains, carefully developed to require nutrients that are not encoun- 
tered in natural environments. Moreover, in the absence of these re- 
quired compounds the cells not only fail to grow, they are rapidly 
suicidal : If they accidentally infected a laboratory’ worker they would 
all die within a' few hours. Hence recombinants made with such strains 
could not conceivably spread. Moreover, experiments in the past year 
have shown that the chance of escape of the recombinant genes from 
these dying bacteria into healthy ones is infinitestimal. 
''Recombinant DN A is increasingly recognized as a tool of great 
versatility. . . . We will be paying an extravagant price if we perpetu- 
ate restrictions that aren't justified by the hazards .'' 1 
Fifth, the present guidelines consider incorporation of the DXA of 
a virus into bacteria especially dangerous. But to cause disease, that 
DXA would have to be released from the host bacterium as naked 
DXA, which would then have to infect a human cell. This probability 
is also exceedingly low, for we know that the naked DXA of a virus 
is less infectious than the same DXA inside the viral coat, bv as much as 
a million-fold. Recognizing these facts, European biologists are rec- 
ommending great relaxation of the guidelines for virus-bacterial re- 
combinants — much greater than that contemplated in this country. 
Hence excessive restrictions may cause this country to fall behind 
rapidly in this important area of medical research. 
My sixth point concerns the class of recombinants containing hu- 
man DXA. These have particularly broad promise for medical re- 
search; but they have been classified as particularly dangerous, be- 
cause of fear that they might pick up and spread the genes of human 
viruses. But this fear is based on the additional assumption that these 
recombinants would be an entirely novel class of organisms, never 
encountered before in nature. "With further discussion this assump- 
tion has become exceedingly unlikely. We know that bacteria can 
take up DXA (though infrequently) : and since bacteria have been 
growing in the colons of our ancestors for millions of years, it is vir- 
tually certain that they have often taken up human DXA. released 
from dying cells of the surrounding intestinal wall. Accordingly, man- 
kind must have long been exposed to recombinants of this kind. 
Finally, the initial discussions not onlv neglected relevant prin- 
ciples of infectious disease, they also failed to take into account well- 
established evolutionary principles, which are essential for under- 
standing the spread of any novel organisms. 
Specifically, bacteria in great variety compete for survival and 
multiplication on various parts of our body, on plants and in the soil. 
The successful strains are those that are best adapted to a given loca- 
tion, and to be well-adapted they must have a well-balanced set of 
genes. 
STATURAL SELECTION 
This adaptation, and this balance, have been evolved over billions 
of years, by natural selection: it is a process that moves in small steps 
and that perpetuates only the tiniest fraction of all the genetic novelty 
[Appendix B — 317] 
